1. SQL: Structured Query Language
Instructor: Mohamed Eltabakh

2. SQL Language Data Definition Language (DDL)
Create tables, specifying the columns and their types of columns, the primary keys, etc.
Drop tables, add/drop columns, add/drop constraints – primary key, unique, etc.
Data Manipulation Language (DML)
Update, Insert, Delete tuples
Query the data
These are already covered
Our focus today

3. Reminder About DDL Create “Students” relation
Create “Courses” relation
CREATE TABLE Students
(sid: CHAR(20) Primary Key,
name: CHAR(20) Not NULL,
login: CHAR(10),
age: INTEGER,
gpa: REAL);
CREATE TABLE Courses
(cid: Varchar(20) Primary Key,
name: string,
maxCredits : integer,
graduateFlag: boolean);
Create “Enrolled” relation
CREATE TABLE Enrolled
(sid: CHAR(20) Foreign Key References (Students.sid),
cid: Varchar(20),
enrollDate: date,
grade: CHAR(2),
Constraints fk_cid Foreign Key cid References (Courses.cid));
Alter Table Enrolled Add Constraints fk_cid Foreign Key cid References Courses(cid));

4. Reminder About: Insert, Update, Delete
This is performed using Data Manipulation Language of SQL (DML)
Insertion
Insert into Students values (‘1111’, …);
Deletion
Delete from Students;
Delete from Students Where sid = ‘1111’;
Update
Update Students Set GPA = GPA + 0.4;
Update Students Set GPA = GPA Where sid = ‘1111’;

5. SQL Query Language SELECT Statement

6. Relation between Algebra and SQL-Select
Will be mapped to the algebraic operators that we learned
SELECT <projection list>
FROM <relation names>
WHERE <conditions>
GROUP BY <grouping columns>
HAVING <grouping conditions>
ORDER BY <order columns>;

7. SELECT-FROM-WHERE π SELECT <list of columns>σ
relation name
SELECT <list of columns>
FROM <relation name>
WHERE <conditions>;

8. SELECT-FROM-WHERE SELECT * FROM Student
* Means “project all attributes”
SELECT *
FROM Student
WHERE sName= ‘Greg’ AND address=‘320FL’;
Must terminate with ; to execute
Student
sNumber
sName
address
professor 1
Dave
311FL MM 2
Greg
320FL 3
Matt ER
sNumber
sName
address
professor 2
Greg
320FL MM
 (sName=‘Greg’ AND address=‘320FL’) (Student)

9. SELECT-FROM-WHERE SELECT sNumber FROM Student
WHERE sName=‘Greg’ AND address=‘320FL’;
Student
sNumber
sName
address
professor 1
Dave
311FL MM 2
Greg
320FL 3
Matt ER
sNumber
sName
address
professor 2
Greg
320FL MM
πsNumber((sName=‘Greg’ AND address=‘320FL’) (Student))

10. Select-From Query Only SELECT and FROM clauses are mandatory
The WHERE clause is optional
If not exist, then all records will be returned (there are no selection predicates)
SELECT <list of columns>
FROM <relation name>;

11. Select-From Query SELECT sNumber, sName FROM Student;
address
professor 1
Dave
320FL MM 2
Greg 3
Matt ER
sNumber
sName 1
Dave 2
Greg 3
Matt
 (sNumber, sName) (Student)

12. Extended Projection SELECT <list of columns or expressions>
The select clause can have expressions and constants
SELECT <list of columns or expressions>
FROM <relation name>
WHERE <conditions>;
Can also rename the fields or expressions using “AS” keyword

13. Extended Projection SELECT ‘Name:’ || sName AS info, 0 AS gpa
FROM Student
WHERE address=‘320FL’;
Student
sNumber
sName
address
professor 1
Dave
320FL MM 2
Greg 3
Matt ER
info
gpa
Name:Dave
Name:Greg
Name:Matt
 (info  ‘Name:’||sName, gpa  0 ) ( (address=‘320FL’) (Student))

14. Mapping between SQL and Relational Algebra
 L ( C (R))
SELECT L
FROM R
WHERE C

15. Renaming Relations and Tuple Variables
SELECT S1.sNumber AS num
FROM Student S1
WHERE S1.sNumber >= 1;
Tuple variable
Student
sNumber
sName
address
professor 1
Dave
320FL MM 2
Greg 3
Matt ER
num 1 2 3
 (num  S1.sNumber) ( (S1.sNumber >= 1) (S1(Student)))

16. Where Clause The comparison operator depends on the data type
For Numbers:
<, >, <=, >=, =, <>
What about Strings??
SELECT S1.sNumber AS num
FROM Student S1
WHERE S1.sNumber >= 1;

17. String Operators
Comparison Operators based on lexicographic ordering: =, <, >, <>, >=, <=
Concatenation operator: ||
Pattern match: s LIKE p
p denotes a pattern
Can use wild characters in p such as _, %
_  matches exactly any single character
%  matches zero or more characters
SELECT ‘Name:’ || sName
FROM Student
WHERE address=‘320FL’;

18. String Matching Example
SELECT s1.sNumber AS num
FROM Student S1
WHERE s1.sName LIKE ‘Da%’
Or S1.professor LIKE ‘M_’ ;
sNumber
sName
address
professor 1
Dave
320FL MM 2
Greg 3
Matt ER
sNumber 1 2

19. Set Operators in SQL Set Semantics Bag Semantics
Union, Intersect, Except
Bag Semantics
Union All, Intersect All, Except All
The two relations R and S must have the same number of columns and data types (Union Compatible)
Oracle allows columns to have different names

20. Example Operators : UNION, INTERSECT, and EXCEPT
(SELECT sName FROM Undergrad_Student)
UNION
(SELECT sName FROM Grad_Student)
If two students have the same name, it will keep only one
(SELECT sName FROM Undergrad_Student)
UNION All
(SELECT sName FROM Grad_Student)
Will keep all names even if identical

21. Set Operations in SQL: Example

22. Example Queries SELECT * FROM loan WHERE amount > 1200 ;
SELECT L.loan_number
FROM loan L
WHERE L.amount > 1200 ;

23. Example Queries SELECT customer_name FROM depositor Union
FROM borrower;